Mesothelioma Aid

Cooper, Hart, Leggiero & Whitehead

Brachytherapy for treatment of mesothelioma

Brachytherapy is a form of radiotherapy
and considered an advanced form of cancer treatment. This therapy
has been in use for more a century; doctors used it in some circumstances
as an alternative to external radiotherapy and surgical treatment.

Radiotherapy is the use of ionizing radiation like x-rays to treat
cancers by killing the cancer cells. About 40% of cancer patients
have radiotherapy as part of their cancer treatment, including those with malignant mesothelioma. Radiotherapy
is used both to treat the cancer and to provide symptomatic relief,
if a cure is not possible. There are two types of radiotherapy:

External radiotherapy or tele-radiotherapy in which the radiation
is delivered from a radioactive source outside the body, usually
a linear accelerator.

Brachytherapy or internal radiotherapy

Brachytherapy is a form of radiotherapy in which the radiation
if given by putting the radioactive source inside the body. ”Brachy”
means short and hence brachytherapy means therapy given at short
distance – ‘localized’ to be precise. It is also
called internal radiotherapy, sealed source radiotherapy, seed implantation
radiotherapy or endocurietherapy. The radioactive source is usually
placed inside the cancer tissue or near to it. The radioactive source
emits ionizing radiation which kills the surrounding cancer cells.
The ionizing radiation can penetrate only a small distance of about
1 cm. So the ionizing radiations of the radioactive source (radio-active
seeds) which is placed in the cancer tissue attack only the surrounding
cancer cells and never attack the normal cells outside the cancer
tissue. The radioactive seeds that are used in brachytherapy are
– Iodine 125, Iodine 131, Palladium 103 and Iridium 192.

Types of brachytherapy

Temporary brachytherapy: The radioactive material
is placed for a specific period of time and then removed. The
radioactive material is placed inside the cancer tissue or near
it and a high dose rate (HDR) or a low dose rate (LDR) radiation
is given.

Permanent brachytherapy: The radioactive seeds
or pellets which are about the size of rice grains (4 mm by 0.8
mm in dimension) are implanted in the cancer tissue or near it.
These seeds are left permanently in the tissue. The seeds slowly
emit radiation which kills the surrounding cancer cells. Up to
100 radioactive seeds are implanted. The radioactivity of the
seeds diminishes gradually over a period of time and eventually
ceases to emit any radiation. The seeds remain in the place of
implantation for life harmless foreign bodies.

Preparing the patient for brachytherapy

Since brachytherapy is given under anesthesia, a few tests are
done to assess the fitness of the patient to undergo anesthesia.
These tests include a few blood tests, chest x-ray and electrocardiography.
The results of these tests allow the anesthesiologist to determine
the type of drug to be used while giving anesthesia. Imaging
studies like ultrasound scan are then done to determine the
location, size and extent of the tumor. This allows the radiotherapist
to decide the location where the radioactive seeds will be placed.

Brachytherapy team

Radiation oncologist – Evaluates the patient and determines
the type of treatment. Responsible for deciding the overall treatment
plan which includes the area to be treated and the dose to be delivered

Radiation physicist – Calculates the dose to be prescribed
and determines the technique to be used to deliver the prescribed
dose

Dosimetrist – Calculates the dose to be prescribed and helps
in delivering the prescribed dose

Radiation therapist – Operates the equipment and delivers
the prescribed dose
Imaging methods like x-rays, ultrasound scan and CT scan are used
to determine the area to be treated and a computer is used to calculate
the time of exposure to radiation and to assist in the introduction
of the radioactive seeds.

The person who manually does the procedure (usually an oncologist)
is also exposed to some amount of radiation. The manual after-loading
is now usually replaced by remote, reducing the risk of exposure
of the oncologist to radiation.

Procedure

Brachytherapy can be either a temporary or a permanent brachytherapy.
And again based on the rate and duration of the therapy, it could
be a high dose rate brachytherapy or a low dose rate brachytherapy.

High dose rate brachytherapy

In high dose rate (HDR) brachytherapy, thin catheters are first
introduced in to the tumor to be treated. These catheters are connected
to afterloader. The afterloader contains the radioactive seeds at
the end of a wire. The seeds are pushed one by one in to the catheters.
The computer decides the time and place of delivering the radiation.

High dose rate brachytherapy is an outpatient procedure. The delivery
of each dose may last for a few minutes. Multiple such doses are
given. Patients may receive up to 12 separate HDR brachytherapy
treatments over one or more weeks. High dose rate brachytherapy
is usually a temporary brachytherapy. After a series of treatment,
the catheters are removed.

Low dose rate brachytherapy

In low dose rate brachytherapy, the patients receive continuous
radiation over a period of hours or days. It is done as an inpatient
procedure to allow the device to work over a longer period of time.
If it is a temporary therapy, the device is removed after series
of treatments. In permanent brachytherapy, the seeds are left in
place which slowly lose the radioactivity over a period of time.

Side effects of brachytherapy

Though brachytherapy is a safer alternative to external radiotherapy
and surgical treatment of cancer, there are a few side effects associated
with this procedure.

Immediately after the procedure, the patient may feel soreness and
pain at the site of the procedure. The treated area may also be
swollen causing discomfort for the patient. Short term side effects
may last for a couple of days and include bleeding from the site.